• A patient with a history of allergic reaction to an antibiotic cream (Mycolog [mixture of nystatin, neomycin sulfate, gramicidin, and triamcinolone acetonide]) was treated with aminophylline. A generalized exfoliative dermatitis resulted. The reaction was attributable to ethylenediamine hydrochloride, which is a component of both agents. Recognition of the potential for systemic medications to induce similar reactions in patients who are allergic to related topical preparations is important when prescribing systemic agents.